1. Field
This invention relates to transmission and speed reducers, and more particularly to a variable speed transmission for adjusting the output of a drive shaft. The device enables the user to optimally set the torque input from a power source and then vary the torque output of the drive train by adjusting the rotational speed via the variable speed transmission.
2. State of the Art
Various transmissions and speed reducers are known. W. C. Pitter, U.S. Pat. No. 1,543,791 discloses a transmission gearing system utilizing a plurality of plungers cooperatively associated with a transmission gearing comprising a circumferentially toothed element. The plungers are reciprocated by an offset cam of fixed displacement to push against the toothed element; thereby moving said element in response to the action of the plungers. Pitter does not provide a variable speed transmission. Its torque ratios are fixed by the number of teeth in relationship to the number of plungers.
J. W. Rabek, U.S. Pat. No. 3,468,175, dicloses several transmission embodiments. The most relevant embodiment discloses a transmission utilizing a wave gear coupled with reciprocating elements activating an undulating surface of the wave gear in response to the action of a fixed displacement cam. Either the wave gear or reciprocating elements may function as an input driving element. The torque ratios of the transmission are determined by the ratio of the number of waves in one gear to the number of reciprocating elements. The Rabek fluid column oscillator embodiment provides a variable speed transmission altering the torque outputs by adjustment of the displacement of the fluid column oscillators. However, it requires complex hydraulic circuitry and timing means to properly displace the fluid column oscillators.
Huska, U.S. Pat. No. 3,472,097 discloses a reversible speed reducer utilizing two relatively rotatable control elements and a driving element with circumferentially spaced bearings. The control elements are preferably of sinesoidal form, with one acting as a rotatable and concentric driving element, and the other as an eccentric spaced bearing element. Said device provides reversibility of rotation of a drive shaft. The cage like configuration is utilized to adjust the path of the bearings as the relative position of the sinesoidal tracks of the control elements are varied affecting the speed output as well as countering the eccentric movement of the driving element in a reverse mode.
E. V. Sundt, U.S. Pat. No. 2,874,594, discloses another speed reducer. The principal object of Sundt is to provide an improved differential type speed reducer which achieves high efficiencies of over 90 percent. Sundt interposes rolling elements, such as balls and rollers, between the oscillating members of rotor and gear members to reduce frictional losses.
F. W. Seek, U.S. Pat. No. 1,449,352, discloses a greater planetary transmission utilizing three annular members concentric about a common shaft. One of said members is stationary and the other two revolve around the shaft. The outer and inner members are spaced apart and provided with opposed cam surfaces and an inner member comprising an annular body in which are journaled a series of rollers. The device provides fixed output based upon the number of rollers and displacement of said rollers along the annular member.
Cited for general interest is Woodling, U.S. Pat. No. 4,394,112, disclosing a combination roller set having roller teeth with concave surfaces disposed to engage one another.
None of the above inventions disclose a variable speed transmission utilizing a variable displacement cam mounted on a drive shaft which selectively forces a series of circumferentially mounted retractable push rods or bearings against the periodic track of a journal mounted casing causing the casing to rotate proportionally to the degree of cam displacement.